Titanium, pure and especially in the form of a titanium base alloy, has properties of lightness, mechanical strength and high temperature resistance which explain that its use is increasing in numerous technical fields, particularly for aircraft construction. As a rule, titanium parts are formed by powder metallurgy. Titanium powder containing additional elements is used. The part is densified by drawing, or isostatic compression and a heat treatment is carried out. Up to now it has been felt preferable to carry out the heat treatment at a temperature lower than the point of transformation to phase .beta., for beyond this point there is an excessive increase in size of the metallurgical grains, which increase detrimentally affects mechanical properties, for example the ductility and tensile strength of the product obtained, even after a partial return from the single .beta. phase to a .alpha. phase during cooling to ambient temperature after the heat treatment.
On the other hand, operating at a temperature lower than the transformation point means waiving the advantages offered by the acicular type structure associated with the partial transformation of phase .beta. obtained at high temperature to phase .alpha.. Such advantages include improved resistance to sudden propagation of cracks (i.e. the tensile strength of the alloy), to the propagation of fatigue cracks, to creep, to corrosion under tensile stress in salt water.